tokina 11-16mm f/2.8 availability?

hi there, can anyone explain why the above lens is in such short supply everywhere? It has been out of stock at b&h, adorama and many more popular sites for quite a while now with the only sites i have found with stock selling for very high prices. What's going on? Is tokina going out of business? Are they replacing this lens despite it only being launched 2007? I heard a batch of this lens was problematic/faulty, are they having quality assurance issues? I would really like this lens at a reasonable price. Anyone with any info. Would be a great help.